1. Field of the Invention
The present invention concerns generally a hydrostatic actuated electrical circuit limit device. In particular, the present invention is directed to a tamper-proof acoustic hydrophone electrical signal limiting shunt switch; the shunt switch apparatus situated within the body or housing of and connectively conjoined with an associated hydrophone, imperatively quenching and preventing any signal transmission from the associated hydrophone when the hydrostatic pressure of the surrounding environment of the hydrophone exceeds a predetermined value, thereby rendering the hydrophone inoperative at or below a predetermined depth.
2. Description of the Related Art
There are many instances when it is desired to control the operation and functioning of an apparatus by means of a pressure sensor, such instances typically involving mechanical pressure, air pressure, or hydrostatic pressure. More particularly, in a maritime or aquatic environment, hydrostatic pressure sensors are often used, for example, ignition of a depth charge or the opening of a conduit to a sample bottle to obtain a sample of seawater at a desired depth. Typically, such devices are “single event” devices and do not employ electrical circuitry, that is, once the initial event has occurred the device either explodes or there is no need for a subsequent sampling event.
However, there are also numerous instances where hydrostatic switches are employed in conjunction with an electrical circuit. Such switches can be broadly categorized into fluid flow control or operating safety.
Hydrostatic flow control switches can be found in water purification and supply systems. For example, U.S. Pat. No. 4,922,067 “Fluid Pressure Switch Having Venting Means For Dispersing Back Pressure” by H. L. West utilizes deformation of laminated conducting and nonconducting materials to detect changes in water pressure. In similar manner, U.S. Pat. No. 4,931,601 by W. J. Lavender also uses a combination of insulating and conducting materials to sense changes in water pressure. Such devices are generally designated for use on land.
Safety at sea and on the water is always a prime concern of those who are in any way involved in a maritime environment. Consequently, many devices used on or under the sea incorporate an ancillary safety device for protection. Such pressure sensors often control an electrical circuit, turning the apparatus either on or off, initiating, igniting, or preventing a potentially dangerous function from occurring.
For example, U.S. Pat. No. 4,495,849 “Remotely Activated Cable Cutter” by M. W. Cooke et al. includes an electrically connected pressure switch “designed to inactivate the apparatus beyond a preset ocean depth”. A detailed description of the switch is absent; presumably, it is a conventional switch proper. Another example of a hydrostatic pressure switch incorporated in an apparatus intended for use under water is U.S. Pat. No. 4,050,382 “Electrically Detonated Explosive Device” by J. M. Power. In both cases, the hydrostatic actuated electrical limit switch is ancillary to the predominant purpose of the apparatus, that is, either severing an underwater cable or igniting an explosive device. These aforementioned inventions are incorporated herein by reference for purposes of indicating the background of the present invention or illustrating the mature state of the art.
In marked contrast to the aforementioned patents, the purpose of the present invention is not ancillary, but a major fail-safe, tamper-proof component of a hydrophone, incorporated therein to nondestructively limit the operating depth of that hydrophone to a predetermined depth.